The present invention relates to a method of performing drilling in earth layers with. simultaneous forcing in of casing tubes of plastic or similar material, and a casing shoe for bringing the casing tube with it.
When performing drilling in earth layers one uses a pilot drill bit with a reamer drill bit arranged such that it can be thrown out eccentrically relative to the pilot drill bit and enlarge the hole drilled thereby. Through this the drilled hole can get sufficient dimension to give place, in addition to the drill bit with retracted reamer, for a casing tube entered into the borehole at the same time as the hole is drilled, The casing tube is thereby driven down by a casing shoe welded to the end of the casing tube and acted on by a down-the-hole hammer. The casing tubes normally consist of three meter long steel tubes which are welded to each other when drilling and the tube has been driven down to a suitable level.